A conventional shower head assembly is shown in FIG. 1 and generally includes a shower head 50 having a shower face with a plurality of holes at one end and an inlet 51 is defined in the other end of the shower head 50. A water control volume control device 40 is engaged with the inlet 51 and includes a restriction member 41 which includes several pawls to hold a mediate member 42 which includes three passages 421 and a cone-shaped tip, and a ring 43 is located at the opening of the inlet 51 to position the restriction member 41 and the mediate member 42. Water enters the inlet 51 and passes through the passages 421 and sprays from the shower face. The size of the passages 421 is not adjustable so that the water volume passing through the passages 421 are varied when the water pressure changes.
The present invention intends to provide a water volume control device which changes the size of the path according to the water pressure so as to control the net water volume of the shower head less than 2.5 gallon per minute.